Apparatus and method for generating visible signal according to amount of data transmission in visible light communication system

ABSTRACT

A method and apparatus are provided for generating a visible light signal according to an amount of data transmission in a first Visible Light Communication (VLC) device. The method includes determining a ratio of an amount of data that has been received from a second VLC device to a total amount of data to be received; determining a visible light signal pattern corresponding to the ratio; generating a visible light signal corresponding to the visible light signal pattern; and outputting the visible light signal.

PRIORITY

This application is a Continuation of U.S. Pat. No. 12/776,087, whichwas filed in the U.S. Patent and Trademark Office on May 7, 2010, issuedas U.S. Pat. No. 9,281,894 on Mar. 8, 2016, and claims priority under 35U.S.C. §119(a) to Korean Patent Application Serial Nos. 10-2009-0040396and 10-2010-0003734, which were filed in the Korean IntellectualProperty Office on May 8, 2009 and Jan. 15, 2010, respectively, theentire disclosure of each of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a Visible Light Communication(VLC) system, and more particularly, to a method and apparatus forgenerating a visible signal to enable a user to confirm the amount ofdata transmission while receiving data.

2. Description of the Related Art

VLC refers to a wireless communication technique using light within avisible light wavelength region. Recently, with the spread of LightEmitting Diodes (LEDs), extensive research is being conducted into VLCtechnologies. In the general VLC system, a transmitter sends visiblelight using an LED or a Laser Diode (LD) as a light source and areceiver processes the visible light using a Photo Detector (PD) etcInfrared communications use similar techniques to those of a VLC system.FIG. 1 is a flow chart illustrating a data transmission process in ageneral wireless communication system using infrared rays. Asillustrated in FIG. 1, wireless communication using infrared raysincludes an infrared communication activation process 101, an externalinfrared communication device search process 102, a communication schemedetermination process 103, a connection process 104, a data transmissionprocess 105, a connection release determination process 106, and acommunication connection release process 107. Through such a series ofprocesses, a user arranges a communication link by directing light to aninfrared communication device.

A data transmission scheme between a transmitter and a receiver thatperform infrared communication is described with reference to FIG. 2.FIG. 2 is a diagram illustrating a data transmission scheme in a datalink layer of an infrared wireless communication system. A transmitter201 transmits data to a receiver 202 in step 203. If the data issuccessfully received, the receiver 202 transmits an ACKnowledgement(ACK) signal as a response to the reception of the data in step 204. Inthis way, data transmission is performed between the transmitter 201 andthe receiver 202. However, since a user cannot directly confirm acommunication state or communication channel state between devices, eventhough a link is disconnected in the middle of transmitting data betweencommunication devices after the communication link is established, theuser has no way of knowing the status of the communication link state.

VLC which is being currently developed is different from infraredcommunication in that it considers such a problem. Namely, the mostdistinctive feature of VLC contrasted with infrared communication isthat VLC enables a user to be able to directly confirm a link state byusing a light source of a visible light band. Therefore, a user cancontrol the direction of a light signal so that light is directed to atarget device even in the process of forming the communication link.

Since infrared communication uses wavelengths of the invisible lightband, a communication link is invisible to a user and therefore a usercannot know a situation in which communication is performed. However,VLC uses a light source of a visible light band so that a user canvisually confirm a communication channel state. In a communicationscheme using visible light as a light medium, there is a need formethods using visible light in various ways and, in this case, theconvenience of a user should be first considered. For example, if a usercan intuitively know a transmission degree of data, that is, thetransmission amount or transmission ratio of data while data istransmitted and received, the convenience of a user will increase.

SUMMARY OF THE INVENTION

An aspect of the present invention is to address at least theabove-mentioned problems and/or disadvantages and to provide at leastthe advantages described below.

Accordingly, an aspect of the present invention provides an apparatusand method for enabling a user to confirm the amount of datatransmission in data communication between two or more VLC devices usingVLC.

In accordance with an aspect of the present invention, a method isprovided for generating a visible light signal according to an amount ofdata transmission in a first Visible Light Communication (VLC) device.The method includes determining a ratio of an amount of data that hasbeen received from a second VLC device to a total amount of data to bereceived; determining a visible light signal pattern corresponding tothe ratio; generating a visible light signal corresponding to thevisible light signal pattern; and outputting the visible light signal.

In accordance with another aspect of the present invention, a firstVisible Light Communication (VLC) device is provided for generating avisible light signal according to an amount of data transmission. Thefirst VLC device includes a VLC receiver configured to receive datathrough the VLC; a data processor configured to determine a ratio of anamount of data that has been received from a second VLC device to atotal amount of data to be received, determine a visible light signalpattern corresponding to the ratio, and generate the visible lightsignal corresponding to the visible light signal pattern; and a VLCtransmitter configured to output the visible light signal.

In accordance with another aspect of the present invention, a method isprovided for generating a visible light signal according to an amount ofdata transmission in a first Visible Light Communication (VLC) device.The method includes determining a ratio of an amount of data that hasbeen transmitted to the second VLC device to a total amount of data tobe transmitted; determining a visible light signal pattern correspondingto the ratio; generating a visible light signal corresponding to thevisible light signal pattern; and outputting the visible light signal.

In accordance with another aspect of the present invention, a firstVisible Light Communication (VLC) device is provided for generating avisible light signal according to an amount of data transmission. Thefirst VLC device includes a VLC transmitter configured to transmit datato a second VLC device through the VLC; and a data processor configuredto determine a ratio of an amount of data that has been transmitted tothe second VLC device to a total amount of data to be transmitted,determine a visible light signal pattern corresponding to the ratio,generate a visible light signal corresponding to the visible lightsignal pattern, and control the VLC transmitter to output the visiblelight signal.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the present invention will be more apparent from thefollowing description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a flow chart illustrating a data transmission process in ageneral wireless communication system using infrared rays;

FIG. 2 is a diagram illustrating a data transmission scheme in a datalink layer of an infrared wireless communication system;

FIG. 3 is an internal block diagram of a VLC device according to anembodiment of the present invention;

FIGS. 4A and 4B are diagrams illustrating visible signal transmissionprocesses depending on a variation of the amount of data transmissionaccording to an embodiment of the present invention;

FIG. 5 is a block diagram of a transmitting-side VLC device and areceiving-side VLC device in a VLC system according to an embodiment ofthe present invention;

FIGS. 6A and 6B are diagrams illustrating visible signal transmissionprocesses depending on a variation of the amount of data transmissionaccording to another embodiment of the present invention;

FIG. 7 is a flow chart illustrating a control process of an outputpattern of visible light according to the amount of received data in areceiving-side VLC device;

FIG. 8 is a diagram illustrating a visible signal transmission processby a comparison of the total amount of data with the amount oftransmitted data in a transmitting-side VLC device according to anotherembodiment of the present invention; and

FIG. 9 is a diagram illustrating a visible signal transmission processby a comparison of the total amount of data with amount information ofdata received from a receiving-side VLC device according to anotherembodiment of the present invention.

Throughout the drawings, the same drawing reference numerals will beunderstood to refer to the same elements, features and structures.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE PRESENT INVENTION

Reference will now be made in detail to the embodiments of the presentinvention with reference to the accompanying drawings. The followingdetailed description includes specific details in order to provide athorough understanding of the present invention. However, it will beapparent to those skilled in the art that the present invention may bepracticed without such specific details.

The present invention provides a method for informing a user of theamount of data transmitted in a VLC device. To this end, the methodincludes acquiring the total amount of the data, determining a visiblelight output pattern corresponding to the ratio of the amount oftransmitted/received data to the total amount of data, and generatingvisible light of the determined output pattern.

While data transmission is in process, the amount of transmitted data isincreased. Then visible light of gradually varying output patterns maybe generated so that a user can intuitively confirm the amount of datatransmission. The present invention provides a method for generatingvisible light having gradually varying output patterns according to theamount of received data. In other embodiments, methods using differentcolors and flickering speeds as the gradually varying visible lightoutput patterns are described in detail. In an alternative embodiment, amethod using the intensity, that is, brightness, of visible light as thevisible light output patterns is described in detail.

A structure and operation of a VLC device in a VLC system having theabove-described function are described with reference to FIG. 3. FIG. 3is an internal block diagram of a VLC device according to an embodimentof the present invention.

Referring to FIG. 3, a VLC device includes a VLC transceiver 300, a VLCcontroller 310, and a data processor 320 for confirming the amount ofdata and generating a signal corresponding to the amount of data. Atransmitting-side VLC device and a receiving-side VLC device may havethe same constituent parts and each of them may generate differentvisible light output patterns depending on the amount of data accordingto an embodiment of the present invention.

More specifically, the VLC transceiver 300 includes a VLC receiver 301and a VLC transmitter 302. The VLC receiver 301 receives data throughvisible light from the transmitting-side VLC device. The VLC transmitter302 transmits desired data to the receiving-side VLC device or generatesan ACK signal as a response to the received data, a signal for informingthe transmitting-side VLC device of the amount of the received data, avisible light signal of different colors, and a visible light signal ofdifferent brightness. The VLC receiver 301 may include a PD whichconverts an externally input visible light signal into an electricsignal. The VLC transmitter 302 may include a visible light LED. The VLCreceiver 301 transmits a visible light signal received from thetransmitting-side VLC device to the controller 310 and transmits asignal input from the controller 301 to the transmitting-side VLC devicethrough the VLC transmitter 302.

The controller 310 includes an Analog-to-Digital (A/D) converter and/ora Digital-to-Analog (D/A) converter 311, a storage unit 312 and amodulating/demodulating unit 313.

The A/D and/or D/A converter 311 converts data received from the VLCreceiver 301 into a digital signal or converts a digital signal which isto be transmitted into an analog signal. Information about the totalamount of received data is converted into a digital signal and then istemporarily stored in the storage unit 312. When data is transmitted,information about the amount of transmitted data is also stored in thestorage unit 312.

The storage unit 312 stores mapping information between a data ratio andcolor information according to an embodiment of the present invention.The storage unit 312 stores mapping information between a data ratio anda flickering interval according to another embodiment of the presentinvention. The storage unit 312 stores mapping information between adata ratio and the brightness (or intensity) of visible light accordingto a further embodiment of the present invention. For example, as a dataratio approaches 100%, mapping information indicating that a flickeringinterval of visible light is gradually increased or decreased is storedin the storage unit 312. In this case, a step at which a data ratio isdivided may be determined according to colors emitted by an LED.Alternatively, a step at which the brightness of visible light that auser can recognize becomes brighter or darker may be determinedaccording to a data ratio. For example, if the LED emits three colors, adata ratio may be divided into three steps corresponding to the threecolors or may be divided into three or more steps using a combination ofthe three colors. Different colors, flickering speeds, or brightness ofvisible light is mapped to respective steps and the mapped informationis stored in the storage unit 312.

The data ratio refers to the ratio of the amount of transmitted orreceived data to the total amount of data. The modulating/demodulatingunit 313 demodulates the converted data into data suitable for a VLCscheme.

The data processor 320 generates a control signal so as to transmit dataand simultaneously to generate visible light of an output patterncorresponding to a data ratio during data transmission. Alternatively,the data processor 320 may generate a control signal so as to transmit avisible light pattern signal at a data non-transmission interval duringdata transmission.

Moreover, the data processor 320 transmits an ACK signal whenever datais received and simultaneously generates a control signal so as togenerate visible light of an output pattern corresponding to a dataratio. Alternatively, the data processor 320 performs a control functionso as to transmit the ACK signal irrespective of the generation ofvisible light of an output pattern corresponding to a data ratio whengeneration of the ACK signal is delayed.

In the receiving-side VLC device, the data processor 320 generates anACK signal as a response whenever data is received and simultaneouslyperforms a control function so as to transmit information about theamount of received data stored in the storage unit 312 to thetransmitting-side VLC device. The data processor 320 includes a dataamount confirmer 321, a processor 322, and a signal generator 323.

The data amount confirmer 321 confirms the amount of data stored in thestorage unit 312 to determine the amount of currently transmitted orreceived data and provides the result to the processor 322. Theprocessor 322 confirms the ratio of the amount of transmitted orreceived data to the total amount of data. The processor 322 determinesa visible signal pattern or a color variation displayed by visible lightcorrespondingly to the confirmed ratio based on the mapping informationstored in the storage unit 312. The signal generator 323 generates acontrol signal for the visible signal pattern or color variation andtransmits the control signal to the VLC transmitter 302. The VLCtransmitter 302 generates visible light of different colors according tothe control signal by using an LED etc.

For example, the signal generator 323 may generate a signal of apredetermined color or a signal of a given flickering pattern accordingto the data ratio confirmed by the processor 322. Namely, the signalgenerator 323 changes a color or pattern of a signal generated accordingto a variation of the amount of data.

It should be noted that the above-described VLC device can generate atboth the transmitting side and the receiving side. Therefore, the VLCdevice shown in FIG. 3 may further include a display for receiving avisible signal and displaying the visible signal using an LD, an LED, oran array thereof. Through the above-described constituent elements, thecases where the VLC device generates a visible signal, using the amountof transmitted data, using the amount of received data, and using theamount of data received from a receiving device after transmitting datahave been described.

A visible signal transmission process depending on a variation of theamount of data transmission according to an embodiment of the presentinvention is described with reference to FIGS. 4A and 4B. Hereinafter, atransmitting-side VLC device will be referred to as a first device 401and a receiving-side VLC device will be referred to as a second device402.

Referring to FIG. 4A, the first device 401 transmits data information,for example, information about the total size (or amount) of data beforetransmitting actual data in step 403. Upon receiving an ACK signal as aresponse to the transmission of the data information, the first device401 transmits data to the second device 402 through a visible lightsignal in step 404. Alternatively, the first device 401 may determinethe amount of the transmitted data, directly determine a visible lightoutput pattern which is to be generated by the second device 402, andinform the second device 402 of the determined visible light outputpattern. In this case, the first device 401 may inform a plurality ofreceiving-side VLC devices of the visible light output pattern.

Then the second device 402 transmits an ACK signal to the first device401 and simultaneously generates visible light of a first color mappedto the amount of received data in step 405. Alternatively, the seconddevice 402 may generate visible light of the visible light outputpattern determined by the first device 401. Here, the second device 402may confirm the remaining transmission amount of data, that is, theamount of data which is to receive based on the information about thetotal size of data. Accordingly, the amount of received data may bereplaced with the remaining transmission amount of data.

Since a data ratio is varied as data transmission is in progress as instep 406, the second device 402 generates visible light of a secondcolor corresponding to the varied data ratio in step 407. In this way,since the ratio of received data is increased while data transmission isin progress, the second device 402 gradually varies colors according tothe varied data ratio and generates visible light of the varied colors.Thus, a user is informed of the amount of data transmission usingvisible light according to the ratio of the amount of received data tothe total amount of data. Therefore, the user can visually confirm theamount of data transmission.

The ACK signal and visible light may be generated by a process differentfrom that shown in FIG. 4A. This transmission process of the ACK signaland visible light is shown in FIG. 4B and the basic data flow in FIG. 4Bis the same as the flow in FIG. 4A. Referring to FIG. 4B, steps 413 and414 are the same as steps 403 and 404 in FIG. 4A. However, if there isdelay in the second device 402 in generating the ACK signal, the seconddevice 402 generates visible light of a third color in step 415irrespective of the ACK signal. As data transmission is in progress asin step 416, the second device 402 generates visible light of a fourthcolor in step 417. In this case, the visible light of a correspondingcolor may continue to be generated until the ACK signal is generated.

As described above, the case where visible light of different colors isgradually transmitted according to a result of comparison of the totalamount of data with the amount of currently received data has beendescribed in conjunction with FIGS. 4A and 4B. The different colors canbe generated by controlling the intensity of Red (R), Green (G) and Blue(B) colors.

This is described with reference to FIG. 5 which illustrates atransmitting-side VLC device and a receiving-side VLC device in a VLCsystem according to an embodiment of the present invention.

In VLC, various colors may be produced by mixing three colors of R, Gand B. To this end, currents or voltages applied to R, G and B LEDs arecontrolled. A controller 501 of the transmitting-side VLC devicegenerates signals for controlling colors which can be emitted by LEDs.The color control signals are converted into analog signals through D/Aconverters 502. The analog signals control LEDs 503 of three colors. Inthis way, the controller 501 generates the control signals for controlthe respective LEDs 503 so as to generate visible light of differentcolors as the amount of received data is increased.

In the receiving-side VLC device, visible light of different colors isreceived through the PDs 504 and is converted into digital signalsthrough A/D converters 505. The converted digital signals are input to acontroller 506.

In the receiving-side VLC device, a specific color may be selectivelyused to maintain an ACK signal which is a response to a transmittedsignal. In this case, a color is varied by adjusting the intensity of acolor except for colors used for signal transmission. Then a receiver ofthe transmitting-side VLC device may receive only a desired color byusing a signal reception filter. In this case, the color used in orderto maintain the ACK signal should not be used for other purposes. Adevice for receiving the ACK signal may use a filter to discriminate thecolor used for the ACK signal. To this end, the PD 504 may use a filterfor discriminating different colors.

FIG. 5 illustrates one embodiment using three colors of R, G and B andthe same description may be applied to different LEDs, other than the R,G and B LEDs, used in an actual VLC device.

In the above-described embodiment of the present invention, a processusing visible light of different colors has been described as a methodfor informing a user of a variation of the amount of data transmission.In another embodiment of the present invention, the method may usedifferent flickering speeds, that is, different flickering intervals ofvisible light.

Visible signal transmission processes depending on a variation of theamount of data transmission according to another exemplary embodiment ofthe present invention are described with reference to FIGS. 6A and 6B.

Referring to FIG. 6A, steps 603 and 604 are the same as steps 403 and404 in FIG. 4A and therefore, a detailed description thereof is omitted.In FIG. 6A, a flickering interval is gradually varied according to theamount of received data based on the total amount of data. Uponreceiving data in step 604, the second device 402 determines aflickering interval mapped to the amount of received data and generatesvisible light at the determined flickering interval together with an ACKsignal as a response to data reception in step 605. Upon receiving thenext data in step 606, since the amount of received data is increased,the second device 402 determines a flickering interval mapped to theincreased amount of data. If the amount of data reaches a data ratio ofa next step at which the flickering interval should be adjusted, thesecond device 402 generates visible light at an adjusted flickeringinterval of the next step as in step 607. In this way, since theflickering interval is gradually varied, a user can confirm a variationof a data transmission rate. For example, if the data transmission rateapproaches 100% while data is transmitted, a flickering speed may befaster or slower to cause a user to confirm the transmission rate.

Unlike FIG. 6A, FIG. 6B shows an ACK signal transmitted separately fromvisible light. Steps 613 and 614 in FIG. 6B are the same as steps 413and 414 in FIG. 4B. In FIG. 6B, if there is delay in the second device402 in generating the ACK signal, visible light is generated separatelyfrom the ACK signal. The second device 402 generates visible lighthaving a flickering speed as in step 615 as data is received. Uponreceiving data in step 616, since the amount of received data is varied,the second device 402 generates visible light having a varied flickeringinterval compared with a previous flickering interval as shown in step617.

A control process for controlling an output pattern of visible lightaccording to the amount of received data in a receiving-side VLC deviceis described with reference to FIG. 7.

Referring to FIG. 7, if a VLC mode is started in step 700, thereceiving-side VLC device initializes a communication link by connectingthe communication link in step 705. Next, the receiving-side VLC devicedetermines whether data information is received in step 710. If the datainformation is received, the receiving-side VLC device determines thetotal amount of data which is to be transmitted by a transmitting-sideVLC device based on the received data information in step 715. If datais received in step 720, the receiving-side VLC device determines anoutput pattern according to the amount of received data based on thetotal amount of data in step 725 and generates visible light of thedetermined output pattern in step 730. The receiving-side VLC devicecontinues to receive data in step 720 unless the communication link isreleased in step 735. In this way, the receiving-side VLC devicegenerates visible light of a gradually varied output pattern as theamount of received data is increased.

Hereinafter, visible signal transmission processes using a comparison ofthe total amount of data to the amount of transmitted/received dataaccording to another embodiment of the present invention are describedwith reference to FIGS. 8 and 9.

FIG. 8 is a diagram illustrating a visible signal transmission processusing a comparison of the total amount of data with the amount oftransmitted data in a transmitting-side VLC device according to anotherembodiment of the present invention. Steps 800 and 810 are the same assteps 403 and 404 in FIG. 4A and therefore, a detailed descriptionthereof is omitted. In FIG.8, an output pattern of visible light becomesdifferent according to the ratio of the amount of transmitted data tothe total amount of data as in steps 815 and 820. The output pattern ofvisible light may be colors, brightness (or intensity) or flickeringintervals of visible light as described previously.

FIG. 9 illustrates a visible signal transmission process using acomparison of the total amount of data with the amount information ofdata received from a receiving-side VLC device. In FIG. 9, the firstdevice 401 transmits data to the second device 402 in step 900 andreceives size information of received data from the second device 402 instep 905. The first device 401 generates visible light of differentoutput patterns according to the ratio of the size of received databased on the received size information to the total size of data as insteps 910 and 925.

Although the certain embodiments of the present invention have beendisclosed for illustrative purposes, various modifications, additionsand substitutions are possible, without departing from the scope andspirit of the invention as disclosed in the accompanying claims.Accordingly, the scope of the present invention should not be limited tothe descriptions of the embodiments above, but defined by theaccompanying claims and any equivalents thereof.

What is claimed is:
 1. A method for generating a visible light signalaccording to an amount of data transmission in a first Visible LightCommunication (VLC) device, the method comprising: determining a ratioof an amount of data that has been received from a second VLC device toa total amount of data to be received; determining a visible lightsignal pattern corresponding to the ratio; generating a visible lightsignal corresponding to the visible light signal pattern; and outputtingthe visible light signal.
 2. The method of claim 1, further comprisingacquiring information indicating the total amount of data to be receivedfrom the second VLC device.
 3. The method of claim 1, wherein generatingthe visible light signal corresponding to the visible light signalpattern comprises generating the visible light signal having colors thatdiffer according to the ratio.
 4. The method of claim 1, whereingenerating the visible light signal corresponding to the visible lightsignal pattern comprises generating the visible light signal havingflickering speeds that differ according to the ratio.
 5. The method ofclaim 1, wherein generating the visible light signal corresponding tothe visible light signal pattern comprises generating the visible lightsignal having color brightness that differs according to the ratio. 6.The method of claim 1, wherein the visible light of the visible lightsignal pattern is simultaneously generated when transmitting anACKnowledgement (ACK) signal.
 7. The method of claim 6, furthercomprising transmitting the ACK signal irrespective of the generation ofthe visible light signal corresponding to the visible light signalpattern, when generation of the ACK signal is delayed.
 8. A firstVisible Light Communication (VLC) device for generating a visible lightsignal according to an amount of data transmission, the first VLC devicecomprising: a VLC receiver configured to receive data through the VLC; adata processor configured to: determine a ratio of an amount of datathat has been received from a second VLC device to a total amount ofdata to be received, determine a visible light signal patterncorresponding to the ratio, and generate the visible light signalcorresponding to the visible light signal pattern; and a VLC transmitterconfigured to output the visible light signal.
 9. The first VLC deviceof claim 8, wherein the data processor is further configured to generatea control signal for generating the visible light signal having colorsthat gradually differ according to the ratio.
 10. The first VLC deviceof claim 8, wherein the data processor is further configured to generatea control signal for generating the visible light signal havingflickering speeds that gradually differ according to the ratio.
 11. Thefirst VLC device of claim 8, wherein the data processor is furtherconfigured to generate a control signal for generating the visible lightsignal having brightness that gradually differs according to the ratio.12. The first VLC device of claim 8, wherein the data processor isfurther configured to generate a control signal to simultaneouslygenerate the visible light signal when transmitting an ACKnowledgement(ACK) signal in response to reception of the data.
 13. A method forgenerating a visible light signal according to an amount of datatransmission in a first Visible Light Communication (VLC) device, themethod comprising: determining a ratio of an amount of data that hasbeen transmitted to the second VLC device to a total amount of data tobe transmitted; determining a visible light signal pattern correspondingto the ratio; generating a visible light signal corresponding to thevisible light signal pattern; and outputting the visible light signal.14. The method of claim 13, further comprising acquiring informationindicating the total amount information of data to be transmitted to thesecond VLC device.
 15. The method of claim 13, wherein generating thevisible light signal corresponding to the visible light signal patterncomprises generating the visible light signal having colors that differaccording to the ratio.
 16. The method of claim 1, wherein generatingthe visible light signal corresponding to the visible light signalpattern comprises generating the visible light signal having flickeringspeeds that differ according to the ratio.
 17. A first Visible LightCommunication (VLC) device for generating a visible light signalaccording to an amount of data transmission, the first VLC devicecomprising: a VLC transmitter configured to transmit data to a secondVLC device through the VLC; and a data processor configured to:determine a ratio of an amount of data that has been transmitted to thesecond VLC device to a total amount of data to be transmitted, determinea visible light signal pattern corresponding to the ratio, generate avisible light signal corresponding to the visible light signal pattern,and control the VLC transmitter to output the visible light signal. 18.The first VLC device of claim 17, wherein the data processor is furtherconfigured to generate a control signal for generating the visible lightsignal having colors that gradually differ according to the ratio. 19.The first VLC device of claim 17, wherein the data processor is furtherconfigured to generate a control signal for generating the visible lightsignal having flickering speeds that gradually differ according to theratio.
 20. The first VLC device of claim 17, wherein the data processoris further configured to generate a control signal for generating thevisible light signal having brightness that gradually differs accordingto the ratio.